1. Field of the Invention
The present invention relates to a method and an apparatus for rendering outlines of multimedia character images, and more specifically, to a method and an apparatus for rendering outlines of multimedia character images for rendering the outlines so as to display, as three-dimensional images, two-dimensional character images appearing when executing multimedia contents such as a game.
2. Description of the Related Art
In effort to display characters as a neat and sweet 3D graphic by representing the characters in a carton style in multimedia contents such as a recently launched game much research has been undertaken. When the outlines are given to the characters appearing according to the execution of the multimedia contents, lines of static or dynamic images are neatly and sweetly treated, such that a viewer can expect to more lively and feelingly use the images. A technology of giving the outlines to the characters is said to be a rendering technology and a type of characters produced by the rendering technology is said to be a carton style.
The rendering technology is said to be a process of feelingly producing the three-dimensional images while considering a shadow, a color tone, a depth, etc., differently displayed on the two-dimensional picture a according to the external information such as a shape, a position, lighting, etc., or a technology of implementing the process. In other words, the rendering is a processing of a computer graphic that changes a shadow, a depth, etc., of a two-dimensionally viewed object to give a three-dimensional effect to the object and adds to the actual sensation of the object. The rendering technology corresponds to a final step when two-dimensional or three-dimensional graphics images are prepared. Generally, in the two-dimensional graphics, the rendering technology indicates a final image processing technology that generates completed images and in the three-dimensional graphics, the rendering technology indicates making model data, which are recorded in a computer, in the form of images so that the model data are described on a display device. The simplest rendering method may include, for example, a wireframe rendering that describes only edges of an object. Further, the most used basic rendering method may include, for example, a raytracing rendering. This is a rendering method that determines color tones of each pixel by a process of reversely tracking a path to a light source from which rays start by calculating the refraction, reflection, etc., of rays. In addition, when rays are randomly reflected, there is a radiosity rendering, etc., that performs rendering while comprehensively considering the relation with other peripheral objects.
Generally, when deriving the outline of the cartoon style, a general method first draws a slight larger black image and then draws an object to be covered thereon, so as to give an outline around the object. Another known method is a method that recalculates positions of all apexes of the outline. For all apexes of the outline, a polygon is generated every time by increasing in a normal vector direction of the apex bit by bit. This method can easily solve an anti-aliasing. However, since this method consumes a lot of resources of a central processing unit (CPU), it has a problem in that a speed of a computer is slow.
The above-mentioned existing rendering methods allocate a lot of CPU resources to make the speed of the computer slow as the outline shape size of the character to be drawn is getting larger.
FIG. 1 is a diagram showing an example where images obtained by performing a rendering processing on characters displayed by executing multimedia contents are displayed on a screen.
The known rendering technologies generally render the outlines of the characters at a uniform thickness without considering a distance of a three-dimensionally displayed character. Therefore, as shown the figure, when the characters are rendered by the known methods, the known methods do not cause any problem for the characters arranged at a close distance, but cannot identify the rendered outlines and can unevenly render the outlines according to the precision of the rendering processing, for the characters arranged at a far distance.